[Elecraft] [K2] PLL reference test failure

[Ilya]

Hi Don!

10pf cap seem to have fixed the problem.
Thanks so much for your help!

And also thanks for the information regarding J310s and J309s! Will be
waiting for your testing results!

73!
Ilya, R3XA

2018-08-27 14:33 GMT+03:00 Don Wilhelm <donwilh at embarqmail.com>:

> Ilya,
>
> I am sorry you are having problems with the PLL Reference Oscillator. Yes,
> there have been several reports of this same failure.
>
> First try a small value capacitor (10 to 15pF) from the source of Q19 to
> ground.
>
> If that does not correct it, can you obtain a J310 FET locally?  If so,
> replace Q19 with it.
>
> The problem seems to be that the J310 FETs in thru-hole format are fast
> disappearing from the market, and the last batch purchased by Elecraft does
> not operate well at the high frequency end of the PLL Reference Oscillator.
> I am currently testing the J309 as a possible replacement.  The testing
> should be completed in the next few days.
>
> One ham with a similar problem wired an SMD J310 on the bottom of the
> board with good results - if you cannot find a thru-hole J310, you might
> consider that solution.
>
> 73,
> Don W3FPR
>
>
> On 8/27/2018 4:47 AM, Ilya wrote:
>
>> Hi Gentlemen!
>>
>> I'm in progress of assembling my first K2 #7837 and now I'm stuck with PLL
>> reference oscillator test. Seems that I've already read all previous email
>> threads regarding similar problems all over the internet - and nothing
>> helped.
>>
>> When I just turn on my K2 after some time it's been off - I'm getting the
>> following figures in PLL reference test (TP3):
>> - Band + is 12099.1 khz
>> - Band - is 12086.15 khz
>>
>> After some time (just a minute or so), the BAND+ value starts drifting
>> down. Drifting slows down with time, but in 2-3 minutes I'm getting 12070
>> or smth like that. If I touch RIT/XIT knob - the value drops even lower -
>> to 12055 or about that.
>>
>>


-- 
best regards, from Ilya Semichastnov, R3XA
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